The social environment and health are closely interwoven. Demographic characteristics, position in social hierarchies, and linkages within social networks and support systems mediate life's challenges, facilitate access to and use of care, and shape health-related behaviors. This biodemographic investigation has two overarching goals. The first is to elaborate the relationships among the social environment, life challenges, and health in an older population. The second is to examine how biological markers of stress and health enhance our understanding of these relationships. Embedded within these two fundamental goals are three specific aims: 1) To incorporate a second round of biomarker collection from persons aged 52 and older in a survey that included the collection of biomarkers in 2000; 2) To exploit the new longitudinal biomarker data to better understand the causal connections among health, the social environment, and exposure to life challenges; and 3) To elaborate the relationships between life challenge and health, exploring how the social environment affects that relationship. We use unusually rich, population-based data from a longitudinal study of older persons. These data have been collected approximately every three years since 1989 and collectively comprise detailed retrospective and current status information on health and on social, economic, and demographic characteristics. The data also include information and archived specimens from a study of a subset of the same population in 2000 including a demographic and health update, assays from blood and urine specimens, and a medical examination. We propose a second round of biomarker collection in 2005 for the survivors of the 2000 cohort as well as for a younger cohort that will be interviewed for the first time in 2003. Our analytical strategy relies largely on two multivariate approaches: 1) generalized linear models for longitudinal data; and 2) grade of membership models. The data from this study will be made available as a public use data set.